With increasing development of scientific technologies, the method for storing documents is changed from the filing of sheet documents to the storage of the documents' electronic files. Generally, a scanning apparatus is a device for scanning the contents of sheet documents into electronic files, which are then stored, processed or spread.
In the early stage, the scanning apparatus can only scan one side of the document. For scanning both sides of the document, after one side of the document has been scanned, the document should be manually turned over so as to scan the other side of the document. However, the process of manually turning over the document is troublesome. For solving the drawbacks, an automatic document feeder is usually integrated into a flatbed scanning apparatus. Consequently, a stack of documents can be successively transported by the automatic document feeder and the duplex scanning operation can be performed by the flatbed scanning apparatus the without the need of manually turning over the documents.
Conventionally, the automatic document feeder and the flatbed scanning apparatus are integrated as a duplex scanning apparatus. This duplex scanning apparatus has a single scanning module for scanning both sides of the document. Since there is only one scanning module, a special mechanism is required to turn over the document after one side of the document has been scanned.
The configurations and operating principles of the conventional duplex scanning apparatus will be illustrated as follows. FIG. 1 is a schematic side view illustrating a conventional duplex scanning apparatus. As shown in FIG. 1, the conventional duplex scanning apparatus 1 comprises a flatbed scanning portion 10 and an automatic document feeder 11. The flatbed scanning portion 10 has a scanning module 101. The automatic document feeder 11 is disposed over the flatbed scanning portion 10. The automatic document feeder 11 comprises a sheet input tray 111, a sheet ejecting tray 112, a sheet pick-up module 113, a sheet transfer channel 114, an inverting region 115, a scanning region 116, plural transfer roller assemblies 117, an inverting channel 118, and a sheet ejecting roller assembly 119.
The process of performing a duplex scanning operation by the conventional duplex scanning apparatus 1 will be illustrated as follows. Firstly, plural documents S are placed on the sheet input tray 111, wherein the first sides of the documents S face upwardly. Then, the sheet pick-up module 113 is contacted with the uppermost document S of the plural documents S to feed the uppermost document S into the sheet transfer channel 114. Then, the document S is transported across a bent zone 1141 of the sheet transfer channel 114 by the transfer roller assemblies 117, so that the first side of the document S faces downwardly. Then, the document S whose first side faces downwardly is moved to the scanning region 116 by the transfer roller assemblies 117. Consequently, the first side of the document S is scanned by the scanning module 101, which is disposed under the scanning region 116. After the first side of the document S has been scanned, the document S is moved to the inverting region 115 by the transfer roller assemblies 117 and the sheet ejecting roller assembly 119. Then, the document S is transported into the inverting channel 118 by the sheet ejecting roller assembly 119 and moved toward the scanning region 116. Consequently, the document S is inverted, and the second side of the document S faces downwardly. Then, the document S whose second side faces downwardly is moved to the scanning region 116 again. Consequently, the second side of the document S is scanned by the scanning module 101.
After the double sides of the document S have been completely scanned, the document S should be inverted again in order to rearrange the scanned document S to be in the same order as the original stack. For rearranging the scanned document S to be in the same order as the original stack, the document S is moved to the inverting region 115 again by transfer roller assemblies 117 and the sheet ejecting roller assembly 119, and the document S is transported into the inverting region 118 by the sheet ejecting roller assembly 119. Consequently, the document S is inverted, and the first side of the document S faces downwardly. Then, the document S is transported across the scanning region 116. At this moment, the first side of the document S is not scanned by the scanning module 101. After the document S is moved to the sheet ejecting tray 112 by the sheet ejecting roller assembly 119 and the first side of the document S faces downwardly, the duplex scanning operation of the document S is completed. The processes of duplex scanning the remaining documents S on the sheet input tray 111 are similar to the process of duplex scanning the first document S, and are not redundantly described herein. After the plural documents S have been scanned, the plural scanned documents S are placed on the sheet ejecting tray 112 in the same order as the original stack, wherein the first sides of the plural documents S face downwardly.
From the above discussions, the document should be transported across the scanning region for three times during the duplex scanning operation is performed by the conventional duplex scanning apparatus 1. Therefore, such a duplex scanning operation is referred as a three-pass scanning operation. The three-pass scanning operation of the conventional duplex scanning apparatus 1, however, is relatively time-consuming. For increasing the scanning speed and the scanning efficiency of the duplex scanning apparatus, another conventional duplex scanning apparatus has been disclosed.
FIG. 2 is a schematic side view illustrating another conventional duplex scanning apparatus. As shown in FIG. 2, the conventional duplex scanning apparatus comprises a flatbed scanning portion 20 and an automatic document feeder 21. The flatbed scanning portion 20 has a first scanning module 201. The automatic document feeder 21 is disposed over the flatbed scanning portion 20. The automatic document feeder 21 comprises a sheet input tray 211, a sheet ejecting tray 212, a sheet pick-up module 213, a sheet transfer channel 214, a scanning region 215, a second scanning module 216, plural transfer roller assemblies 217, and a sheet ejecting roller assembly 218.
The sheet input tray 211 is used for placing plural documents S′ thereon. After the documents S′ are scanned, the scanned documents S′ are placed on the sheet ejecting tray 212. The sheet pick-up module 213 is located beside the sheet input tray 211. When the sheet pick-up module 213 is contacted with the plural documents S′ on the sheet input tray 211, the plural documents S′ can be successively fed into the sheet transfer channel 214. The sheet transfer channel 214 is disposed within the automatic document feeder 21, and arranged between the sheet input tray 211 and the sheet ejecting tray 212. The sheet transfer channel 214 passes through the sheet pick-up module 213 and the scanning region 215. The scanning region 215 is disposed over the first scanning module 201. When the document S′ is transported across the scanning region 215, the first side of the document S′ is scanned by the first scanning module 201. The second scanning module 216 is disposed over the scanning region 215. When the document S′ is transported across the scanning region 215, the second side of the document S′ is scanned by the second scanning module 216. The plural transfer roller assemblies 217 are disposed in the sheet transfer channel 214 for transferring the plural documents S′ through the sheet transfer channel 214 and transporting the plural documents S′ across the scanning region 215. The sheet ejecting roller assembly 218 is located beside the sheet ejecting tray 212 for transporting the scanning documents S′ to the sheet ejecting tray 212.
The process of performing a duplex scanning operation by this conventional duplex scanning apparatus 2 will be illustrated as follows. Firstly, plural documents S′ are placed on the sheet input tray 211, wherein the first sides of the documents S′ face downwardly. Then, the sheet pick-up module 213 is contacted with the uppermost document S′ of the plural documents S′ to feed the uppermost document S′ into the sheet transfer channel 214. Then, the document S′ is moved to the scanning region 215 by the transfer roller assemblies 217, wherein the first side of the document S′ faces downwardly. When the document S′ is transported across the scanning region 215, the first side of the document S′ is scanned by the first scanning module 201 under the scanning region 215 and the second side of the document S′ is scanned by the second scanning module 216 over the scanning region 215. Then, the document S′ is moved to the sheet ejecting tray 212 by the transfer roller assemblies 217 and the sheet ejecting roller assembly 218, wherein the first side of the document S′ still faces downwardly. Meanwhile, the duplex scanning operation of the document S′ is completed. The processes of duplex scanning the remaining documents S′ on the sheet input tray 211 are similar to the process of duplex scanning the first document S′, and are not redundantly described herein.
Since the document is only transported across the scanning region once during the duplex scanning operation is performed by the conventional duplex scanning apparatus 2, the duplex scanning operation is also referred as a one-pass scanning operation. The conventional duplex scanning apparatus 2 has reduced working time. However, this conventional duplex scanning apparatus 2 is more expensive. In addition, since the second scanning module 216 is installed in the automatic document feeder 21, the height and the overall volume of this conventional duplex scanning apparatus 2 are both increased.